If the fall of the Berlin Wall on November 9th, 1989, is a date etched in the minds of most Germans, the day it went up is far harder for many young people to pin down.
On the morning of Sunday August 13th, 1961, Berliners woke to find their city divided by a physical barrier. The East-West inner German border had been closed - and would remain so for 27 years.
Yet fewer than one third of people under the age of 30 could name the date in 1961 when the East Germans first rolled out the barbed wire entanglements marking the 155-kilometre divide around the western part of the capital.
Overall,19 percent of those polled by the Berlin-based Infratest dimap research institute could hazard no guess at all at the significance of August 13th, when the Communist leadership under Walter Ulbricht implemented its plan to halt the flow of East Germans to the West.
Former GDR citizens were better informed, according to the poll conducted among 1013 people.
Sixty-nine percent of those respondents knew the significance of August 13th, compared to 45 percent of former West Germans.
'Losing the past'
Some might be excused for losing track of the date among other momentous events in the early 1960s, such as Yuri Gagarin's space flight of April 12th, 1961, and the Cuban Missile Crisis, which cast apocalyptic doom over the world for two weeks in October 1962.
But as German newspapers commemorated the date, they lamented the growing lack of awareness of August 13th, as well as trivial commercialization of this integral period of national history.
"The memory of the GDR is being peddled and also reduced to a footnote in our education," wrote Berlin's Tagesspiegel newspaper. "And so we are losing our past."
The sudden physical division of the city was still sombrely marked on Wednesday. Wreaths were laid at the site of the former Wall and groups of Germans and tourists paid respects to the 136 people who died trying to flee from East Berlin across the formidable barrier.
By the time the final modifications to the Wall were completed in 1980, it comprised parallel lines of 3.6-metre concrete panels that were separated by no-man's land that was up to 300 metres wide.
Troops with shoot-to-kill orders manned watchtowers along the construction and patrolled the perimeter with guard dogs. But around 5,000 people still managed to escape.
This November 9th, Germany will mark 25 years since East German authorities gave the order to allow people free passage in 1989. The demolition of the Wall, both official and as a result of trophy hunters, began shortly after.